1. Technical Field
The present invention relates to computer graphics techniques, and relates to an image generating apparatus which generates computer graphics images and an image generating method.
2. Background Art
The process for generating computer graphics (CG) images causes a heavy computational load. For this reason, the information processing apparatus which performs a process for generating images in real time includes an image generating apparatus (graphics processing unit) dedicated to the process for generating images, in addition to the central processing unit (CPU).
FIG. 1 is a flowchart showing general process of the image generating method by a conventional image generating apparatus.
The conventional image generating apparatus in general first loads vertex data of an input polygon model from an information storage device (memory) (S101). Note that the vertex data is composed of the coordinate data indicating a position of a vertex and form data which includes data other than the coordinate data. Next, the coordinate of the coordinate data in the vertex data is transformed to a world coordinate (S102). Furthermore, the coordinate in the world coordinate is transformed to a display coordinate (S103). Subsequently, using the transformed coordinate data, for each polygon composed of the loaded vertex data, it is determined whether the polygon rendering is valid or not by clipping determination for determining whether or not the polygon is in a visible space or by culling determination for determining whether or not the polygon is facing, from the viewpoint, a plane that should be displayed (S104). Only the polygons that have been determined to be valid are rendered using the loaded vertex data (S105). It is determined whether or not processing for all of the polygons are complete (S106), and when the processing is not complete (“Continue” in S106), each process (S101 to S105) is repeated. When the processing for all of the polygons are complete (“Complete” in S106), the image generating apparatus outputs the rendered image.
Examples of the image generating apparatus include the techniques disclosed in Patent Reference 1 and Patent Reference 2.
Patent Reference 1 discloses a technique for non-interactive purposes where certain sequences to be skipped are determined in advance. The technique disclosed in Patent Reference 1 reduces data unnecessary for rendering in advance. This reduces the memory access amount for loading the data.
Patent Reference 2 discloses a technique where a data cache dedicated to load the input polygon data is provided. In the technique disclosed in Patent Reference 2, the vertex data loaded once is stored in the dedicated data cache, and thus the vertex data is not reloaded when the same vertex data is referred to. This reduces the memory access amount.    Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2001-209369    Patent Reference 2: Japanese Unexamined Patent Application Publication No. 2001-195603    Non-Patent Reference 1: “Computer Graphics”, Computer Graphics Arts Society Publishing (Page 34, Page 100)